Multiple crossovers and coherent states in a Mott-Peierls insulator

TL;DR

This paper uses Dynamical Mean Field Theory to explore the complex interplay between Mott and Peierls insulators in a dimer Hubbard model, revealing new insights into phase transitions and electronic structures relevant for materials like VO$_2$.

Contribution

It systematically analyzes the Mott-Peierls crossover and the evolution of electronic states, highlighting the role of intra- and inter-dimer hopping in a correlated insulator.

Findings

Identification of metal-insulator transition lines

Observation of Hubbard bands with mixed character

Relevance to spectroscopic signatures in VO$_2$

Abstract

We consider the dimer Hubbard model within Dynamical Mean Field Theory to study the interplay and competition between Mott and Peierls physics. We describe the various metal-insulator transition lines of the phase diagram and the break down of the different solutions that occur along them. We focus on the specific issue of the debated Mott-Peierls insulator crossover and describe the systematic evolution of the electronic structure across the phase diagram. We found that at low intra-dimer hopping the emerging local magnetic moments can unbind above a characteristic singlet temperature $T^*$. Upon increasing the inter-dimer hopping subtle changes occur in the electronic structure. Notably, we find Hubbard bands of a mix character with coherent and incoherent excitations. We argue that this state is relevant for VO$_2$ and its signatures may be observed in spectroscopic studies, and possibly through pump-probe experiments.